This paper reports an automatically reconfigurable series–parallel switched-capacitor step-down DC–DC converter for neural stimulation applications, fabricated with a 0.13 μm standard complementary metal oxide semiconductor process. The stimulator chip can generate pre-programmed biphasic or dynamically programmed arbitrary current waveforms, up to ±127 μA peak with 7-bit resolution. To improve the power efficiency, the supply voltages of the stimulating current sources are dynamically modulated following the output voltage. The functionality of the stimulator is verified in vitro using parylene-based microelectrode arrays in phosphate-buffered saline.